I am adding dragons to my current world. However my world currently uses a sympathetic style of 'magic' and qualifies to the laws of thermodynamics (much to 'The Kingkiller Chronicles'). In this case, I'm stumped on what could be used for the dragons to attain flight? This is an entire Terra-Formed world, with our style land/sea ratios.
I did view this How could dragons be explained without magic? question. Using a sympathetic link (as quoted from the question) this could work:
hydrogen gas trapped in large pockets within its body to the point that it could fly despite its apparent large size
The dragons would range from babies (several kilos) to large venerable ones (several tonnes). This would mean that following the laws, it would take around 400 litres of hydrogen to lift one pound. But where would they get this from, what sort of area would produce enough hydrogen gas to allow them to create a sympathetic link with it? And would it be possible to do so with the amount they could need?